Allochthonous Input -
Organic material that falls into a stream from the surrounding land is
known
as allochthonous input. Combined with the instream accumulation of primary
production by algae and vascular plants — the autochthonous input —
allochthonous input provides the support system for all instream life.
Allochthonous inputs span a broad range of sizes; from leaf fragments to
branches and entire trees. Although the size range of these inputs is
continuous, individual pieces typically are classified by size and function
and grouped for convenience. Fine paniculate organic material (FPOM)
encompasses all particles that will pass through a .04-inch (1.0-mm) fine
mesh sieve. The largest pieces of wood, known as large or coarse woody
debris (CWD), typically are greater than three feet in length and at least 2
to 4 inches in diameter. In between is CPOM or coarse paniculate organic
material.